Heretofore, the usual practice in continuously concentrating or evaporating liquids has been to heat and evaporate the liquids under pressure or partial vacuum in closed vessels of single or multiple effect evaporators having tube-type calandrias. Some variations have been proposed, such as the multiple effect, concentric shell evaporator disclosed in Thelen et al U.S. Pat. No. 945,640, the multiple plate, oscillating spray distillation apparatus of Hammer et al U.S. Pat. No. 3,211,633, and, for food dehydration, the rotating cone apparatus of Birdseye U.S. Pat. No. 2,521,442 and the multiple effect evaporation by freezing of Toulmin U.S. Pat. No. 2,628,485. However, in general, prior continuous liquid concentrators or evaporators have required expensive equipment and prolonged exposure of the liquid to heat exchange with correspondingly high energy consumption, and, for food concentrates, such as tomato paste, evaporation, particularly under partial vacuum, can detrimentally affect taste, color and vitamin and enzyme content. It is with the solution of these problems in continuously concentrating liquids that the present invention is particularly concerned.